arp-sk: add mirror and test (#25791)

Formula/arp-sk.rb

@@ -2,6 +2,7 @@ class ArpSk < Formula
   desc "ARP traffic generation tool"
   homepage "http://sid.rstack.org/arp-sk/"
   url "http://sid.rstack.org/arp-sk/files/arp-sk-0.0.16.tgz"
+  mirror "http://distcache.freebsd.org/ports-distfiles/arp-sk-0.0.16.tgz"
   sha256 "6e1c98ff5396dd2d1c95a0d8f08f85e51cf05b1ed85ea7b5bcf73c4ca5d301dd"
 
   bottle do
@@ -22,4 +23,8 @@ class ArpSk < Formula
                           "--with-libnet=#{Formula["libnet"].opt_prefix}"
     system "make", "install"
   end
+
+  test do
+    assert_match "arp-sk version #{version}", shell_output("#{sbin}/arp-sk -V")
+  end
 end